TWI593714B - Method for preparing copolymer of ethylene and vinyl alcohol - Google Patents

Description

Method for producing ethylene-vinyl alcohol copolymer

The present invention relates to a method for producing an ethylene-vinyl alcohol copolymer; in particular, the present invention relates to an ethylene and a vinyl ester of a raw material of an ethylene-vinyl alcohol copolymer (hereinafter, also referred to as "EVOH") in an alcohol In the polymerization, a by-product produced during saponification, a residue of a catalyst used in saponification, and a method for producing an ethylene-vinyl alcohol copolymer in which impurities such as an alcohol solvent are highly removed can be used.

Ethylene-vinyl alcohol copolymer (EVOH) is widely used for forming films, sheets, and bottles, etc., because of its excellent transparency, gas barrier properties against oxygen, solvent resistance, oil resistance, and mechanical strength. As various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial pharmaceutical packaging materials, and pesticide packaging materials.

The EVOH is usually produced by a method in which an ethylene-vinyl ester copolymer formed by copolymerizing a fatty acid vinyl ester such as vinyl acetate with ethylene is saponified in an alcohol solvent in the presence of a catalyst under high temperature and high pressure. Manufacturing. In recent years, as a method of producing the above, a method is known in which an alcohol solution of EVOH in a high-temperature and high-pressure state obtained in the saponification step is brought into contact with water or water vapor in a container to replace an alcohol with water. A water/alcohol mixed solution of EVOH which is stable under normal pressure is obtained, and the viscosity is adjusted by adjusting the water/alcohol ratio or pressure, and after melting and kneading by an extruder, it is extruded in a strip shape to be mainly water. A method of forming a film, a sheet, a bottle, or the like by a method of cutting and drying the granules in a coagulation bath of a low-temperature component, and then pulverizing the granules (see Patent Document 1) .

However, the above-mentioned conventional method for producing EVOH has a problem in that it is washed out when the water/alcohol solution of EVOH is extruded into a coagulation bath to form EVOH into a strip shape and the alcohol is washed and removed. The alcohol in the coagulation bath volatilizes into the air, which causes deterioration of the working environment.

Here, as a method for solving the above problems, there has been proposed a method in which a water/alcohol mixed solution of the above-mentioned EVOH which is stable under normal pressure is used before using an extruder to obtain particles of the final product, using a crucible or the like. (The cement composed of a mixture of EVOH and water/alcohol) has a reduced water content. Once granulated, the EVOH aqueous composition particles obtained by washing and drying are used, and then the above extruder is used to obtain the final Finished particles of EVOH (see Patent Documents 2 and 3).

However, the methods disclosed in Patent Documents 2 and 3 have a manufacturing apparatus for drying the EVOH aqueous constituent particles (hereinafter, such particles are referred to as intermediate particles) and a device for drying the intermediate particles, and thus the manufacturing cost. Have an adverse effect. Further, in addition to the time and energy required for the dehydration and drying of the above intermediate particles, there is a difficulty in that the EVOH intermediate particles which are retained for a long time in the dryer are easily thermally deteriorated, because the intermediate particles are mixed into the subsequent finished particles. Or in the forming process, the possibility of becoming a foreign object is increased.

In addition, the EVOH aqueous composition of the intermediate product usually contains a residue of a catalyst used in saponification, a by-product produced by saponification, and an impurity such as an alcohol as a solvent, and when the amount of these impurities is large, The EVOH particles obtained in the final product, and the molded articles such as films, sheets, and bottles using the particles may have a problem of occurrence of color change. However, the above-described EVOH production method (Patent Documents 2 and 3) which is washed after the production of the intermediate particles has a problem that the inside of the particles is to be carried out since the washing is performed in a solid (particle shape) state. The complete removal of impurities is quite difficult.

Here, the present inventors have proposed a method for producing an ethylene-vinyl alcohol copolymer and particles thereof as follows: in the production process of the EVOH composition, in an agitating vessel before using an extruder to obtain particles of the final product. While stirring, the dope (high viscosity dope) composed of a mixture of EVOH and water/alcohol is brought into contact with water, and the dope is made to contain less than 10 parts by weight of the alcohol relative to the weight portion of the EVOH 100 and 20 The composition of water in the range of ~100 parts by weight can obtain an EVOH composition having a low water content without washing and drying under granulation (see Patent Document 4).

Conventional technical literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2002-80605

Patent Document 2: Japanese Laid-Open Patent Publication No. 2002-284811 (corresponding to US Pat. No. 6,830,829)

Patent Document 3: International Publication No. 2004/009313 (corresponding to US 2006108703)

Patent Document 4: International Publication No. 2009/084509 (corresponding to EP 2228405)

However, the method for producing the ethylene-vinyl alcohol copolymer particles proposed by the present inventors (Patent Document 4) can improve the removal rate of impurities compared to the above-described conventional EVOH production method, but after further review, the production method is found. In the case where the EVOH containing the object to be cleaned has high viscosity to the glue of the alcohol, the high-viscosity EVOH glue is stirred while maintaining its shape only by the stirring operation in the water, and the glue is adhered. The water inside the slurry becomes less susceptible to exposure. Therefore, it is possible that the above impurities are not sufficiently removed, and there is a need for improvement.

In view of the above circumstances, an object of the present invention is to provide a method for producing an ethylene-vinyl alcohol copolymer which can efficiently remove impurities such as residues, by-products, and solvents of a saponification catalyst generated during saponification, and is highly efficient. High quality and homogeneous finished product.

In order to achieve the above object, the present invention is directed to a method for producing an ethylene-vinyl alcohol copolymer, comprising a main washing step of introducing a paste comprising an ethylene-vinyl alcohol copolymer and an alcohol into a horizontal washing tank, In this horizontal washing tank, while being in contact with the washing water, a shearing force is applied and kneading is performed to repeatedly replace the surface and the inside of the above-mentioned dope, and a part or all of the above alcohol is washed with water. They were discharged together to the outside of the tank to obtain an ethylene-vinyl alcohol copolymer aqueous composition having a low alcohol content.

That is, the inventors of the present invention have further intensively studied in order to solve the above problems, and have found that the present invention can be completed by almost completely removing impurities in the above-mentioned dope by the following method. That is, by using a high-viscosity cement containing EVOH and an alcohol, not only stirring is carried out in the water, but also shearing force is applied in contact with the washing water, and a forced crucible is applied to make the surface renewed. In order to repeatedly replace the surface and the inside of the above-mentioned dope, the entire gel is in contact with the washing water a plurality of times (that is, in the liquid phase).

Further, in the present invention, the above-described washing step is the focus of the present invention, and it is referred to as "main washing step". In the present invention, the main washing does not mean that there is a difference in the difference between the residence time of the dope and the amount of impurities before and after the washing, and the other washing steps.

The method for producing an ethylene-vinyl alcohol copolymer of the present invention is an invention based on the above knowledge. In other words, the paste containing the ethylene-vinyl alcohol copolymer and the alcohol is introduced into the horizontal washing tank, and is brought into contact with the washing water introduced into the horizontal washing tank, and not only the stirring but the shearing is applied. The force is broken and twisted to repeatedly replace the surface and the inside of the above-mentioned dope, in other words, to perform surface renewal. Therefore, not only the surface of the dope but also the inside thereof is in contact with the washing water, whereby a part or all of the above-mentioned washing water and the above-mentioned alcohol, and residual catalyst and by-products during polymerization and saponification can be removed with high efficiency. Impurities. Therefore, by the method for producing an ethylene-vinyl alcohol copolymer of the present invention, impurities in the aqueous composition of EVOH can be reduced, and the quality of the EVOH of the final product and the molded article using EVOH can be improved.

Further, in the case where the horizontal washing tank is disposed such that the flow direction of the dope in the horizontal washing tank is inclined from the upper side to the lower side, the glue introduced into the trough type container is in the crucible (ie, At the same time, due to the self-weight of the glue itself, it is moved from the side of the glue to the side of the lead (i.e., from the upstream to the downstream) along the inclination, and is taken out of the grooved container by gravity. Therefore, in the method for producing an ethylene-vinyl alcohol copolymer of the present invention, even if the dope has a high viscosity, it can be smoothly passed through the main washing step.

Further, when the bath ratio of the horizontal washing tank is 0.5 to 10 by weight of the introduced washing water/introduction slurry, the water-alcohol substitution, washing efficiency and cost in the horizontal washing tank are The balance of effects is optimal.

Further, the horizontal washing tank has a screw that applies a shearing force perpendicular to the longitudinal direction of the horizontal washing tank, and when the gap of the screw is 1 to 20 mm, the rubber slurry can be further improved. The efficiency of surface updates.

On the other hand, in order to improve physical properties such as heat resistance of the ethylene-vinyl alcohol copolymer, additives such as a carboxylic acid compound, a boron compound, and a phosphoric acid compound may be added to the EVOH, and in the conventional method for producing EVOH, After the EVOH is granulated, the granules are immersed in an aqueous solution containing the above additives, followed by dehydration-drying. However, since the demand for resin performance has become high due to the heightening of the forming technology in recent years, the industry has demanded a technique capable of more uniformly dispersing the above additives in the particles.

In contrast, in the production method of the present invention, in the case where the washing water in the main washing step contains at least one additive selected from a carboxylic acid, a carboxylate, a boron compound, or a phosphoric acid compound, the above-mentioned dope is accompanied. The ruthenium (i.e., surface renewal) allows the above additives to be uniformly dispersed inside the paste. Further, there is no need to provide a step or apparatus for adding the above-described additive, and there is an advantage that the reduction of the manufacturing steps or the simplification of the apparatus can be achieved.

Furthermore, in the present invention, when the water content of the ethylene-vinyl alcohol copolymer aqueous composition obtained in the main washing step is 30 to 400 parts by weight based on 100 parts by weight of the ethylene-vinyl alcohol copolymer, When the EVOH aqueous composition is melted and granulated by an extruder, it is not necessary to use a special extruder such as an extruder having a large L/D value (effective length of the screw/diameter of the screw). advantageous.

Further, if the water content of the aqueous composition of the colloidal ethylene-vinyl alcohol copolymer obtained in the main washing step is too low, the viscosity of the aqueous composition of the ethylene-vinyl alcohol copolymer becomes large, and there is a resin. Conversely, if the water content is too high, the production efficiency at the time of dehydration and drying of the resin tends to decrease.

Next, in the method for producing an ethylene-vinyl alcohol copolymer of the present invention, before the main washing step, a preliminary washing step of introducing a solution containing an ethylene-vinyl alcohol copolymer and an alcohol into a washing container is included And contacting the water or water vapor in the washing container, and discharging a part of the alcohol together with water or steam to the outside of the container to obtain a paste containing ethylene-vinyl alcohol copolymer, alcohol, and water. In this case, the substitution of the alcohol (solvent) and water in the solution can be performed with higher efficiency.

Further, in the method for producing an ethylene-vinyl alcohol copolymer of the present invention, the method for producing granules comprising the ethylene-vinyl alcohol copolymer aqueous composition obtained in the main washing step is supplied to an extruder. After the melting enthalpy is carried out, it is discharged and cut to obtain particles of an ethylene-vinyl alcohol copolymer, in which case the alcohol (solvent) in the solution containing EVOH and alcohol is carried out with high efficiency before the granulation step. With the substitution of water, it is therefore not necessary to carry out the washing of the granules and the accompanying heat drying after the granulation using the extruder. Therefore, the method for producing an ethylene-vinyl alcohol copolymer of the present invention can achieve reduction in the steps of manufacturing EVOH particles and simplification of equipment, and at the same time, the manufacturing cost of EVOH can be reduced by the acceleration or energy saving of the steps.

Further, the water content of the particles of the ethylene-vinyl alcohol copolymer obtained by the above-mentioned step of preparing the particles is preferably less than 10 parts by weight with respect to 100 parts by weight of the EVOH.

Next, an embodiment of the present invention will be described in detail based on the drawings. However, the invention is not limited to this embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing an outline of an aspect of a method for producing an ethylene-vinyl alcohol copolymer of the present invention.

The EVOH manufacturing method comprises the following steps: a saponification treatment step (not shown) for saponifying an alcohol solution of an ethylene-vinyl ester (in this case, an ethylene-vinyl acetate) copolymer, To obtain an alcohol solution of EVOH; a preliminary washing step of contacting a solution containing EVOH and an alcohol with water vapor in a tower-type washing container to obtain a cement comprising EVOH and an alcohol; a main washing step, It applies a shearing force to the glue in the horizontal washing tank and makes it contact with the washing water, so that the inside and the surface of the glue are repeatedly replaced, that is, in the liquid phase, thereby obtaining a glue having a low alcohol content. An EVOH aqueous composition (EVOH-slurry); and a granulation step (not shown) which granulates the washed EVOH aqueous composition using an extruder and a slitter.

The "adhesive containing EVOH and alcohol" (also referred to as EVOH cement) of the present invention is a rubbery (or gel-like) aqueous gel which is a soft and fluidly deformable solid. The EVOH cement can be simply cut into individual pieces by a knife or the like, and the cut individual after the new surface is formed can be combined with other individuals to form a new individual (this can also be repeated). In the present invention, by utilizing the properties of the soft and fluid rubbery EVOH cement, the solid phase is cut and the "surface renewal" of the composite is repeated in the liquid phase, and the cleaning and/or heat stabilizer addition is performed simultaneously. deal with.

A steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the rubber-like EVOH paste 500 g was measured by a falling ball viscosity measurement method (Stoker method); the viscosity of the above EVOH cement was usually 10 ¹ to 10 ⁶ mPa. s, preferably 10 ² to 10 ⁶ mPa ‧ , particularly preferably 10 ¹ to 10 ⁴ mPa ‧ s. The viscosity of the EVOH paste varies depending on temperature, pressure, concentration of the EVOH resin component, and alcohol content. Therefore, in the crucible step used in the main washing step of the present invention, it is necessary to adopt a structure in which the EVOH dope can be repeatedly cut and combined, and a screw type, a gear type, or a vane type or the like described below is usually used.

Further, in the case where the EVOH dope is opaque, a method of calculating the viscosity using a stirring torque value having a correlation with the falling ball viscosity measurement value is used. That is, measuring the falling ball viscosity of 500 g of a plurality of transparent mortars having different viscosities, and under the same conditions, recording the stirring torque value at a certain stirring speed in a glass autoclave having six blades, using the data as a reference, and The stirring torque value of the opaque dope was measured under the same conditions, and the falling ball viscosity measurement value was calculated from the data.

Further, in the present invention, the step of bringing the solution containing EVOH and the alcohol obtained in the saponification treatment step into contact with water vapor in a column type washing container to obtain a dope containing EVOH and alcohol is as described above. "Prepare the washing step." In the present invention, the "preparation washing step" refers to the step before the main washing step, and does not indicate the difference between the residence time of the dope and the amount of impurities before and after the washing, and the other washing step has The difference in relativity.

First, the ethylene-vinyl ester copolymer used in the present invention and the EVOH obtained in the present invention will be described in advance.

The EVOH obtained in the present invention is a water-insoluble thermoplastic resin. The EVOH can be usually obtained by copolymerizing a vinyl ester with ethylene to obtain an ethylene-vinyl ester copolymer, and then saponifying it, and the ethylene structural unit-vinyl alcohol structural unit is mainly composed, and contains a certain amount remaining in the saponification. Vinyl ester building block.

The vinyl ester compound is typically vinyl acetate, and may be used alone or in combination with vinyl acetate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutylate, and the like. Methyl vinyl acetate, vinyl phthalate, vinyl laurate, vinyl stearate, vinyl benzoate, or vinyl versatate.

Further, in the present invention, in addition to ethylene and vinyl ester, copolymerization with a polymerizable ethylenically unsaturated monomer may be carried out within a range not impairing the characteristics necessary for EVOH; Listed below. For example, an olefin such as propylene, 1-butene or isobutylene, 2-propen-1-ol, 3-buten-1-ol, 4-penten-1-ol or 5-hexen-1-ol can be mentioned. a hydroxyl group-containing α-olefin such as 3,4-dihydroxypropene-1-butene, 5-hexene-1,2-diol or propylene, or a mercapto compound or ester compound thereof; as an ester compound Examples thereof include 3,4-dimethoxy-1-butene, particularly 3,4-diethyloxy-1-butene and the like. Further, examples thereof include unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) methylene succinic acid, or salts thereof, and carbon. A number of mono- or dialkyl esters of 1 to 18. Further, examples thereof include acrylamide, N-alkyl acrylamide having 1 to 18 carbon atoms, N,N-dimethyl acrylamide, 2-propene decyl propane sulfonic acid or a salt thereof, and acrylamide. Acrylamine or its acid salt or a quaternary salt thereof, such as acrylamide or isobutyleneamine, N-alkylisobutyleneamine having a carbon number of 1 to 18, and N,N-dimethylisobutylene An isobutylene amide such as an amine, 2-isobutylene decylamine propanesulfonic acid or a salt thereof, and isoammonium propyl dimethylamine or an acid salt thereof or a quaternary salt thereof. Further, examples thereof include N-vinylguanidamine such as N-vinylhydropyrrolidone, N-vinylformamide, and N-vinylacetamide, vinyl cyanide such as acrylonitrile or methacrylonitrile, or carbon number. Halogenated vinyl ethers such as alkyl vinyl ether, hydroxyalkyl vinyl ether and alkoxyalkyl vinyl ether of 1~18, vinyl chloride, vinyl chloride, vinyl fluoride, vinylidene fluoride, ethylene bromide, etc. Vinyl decane such as ethylene or trimethoxyvinyl decane, and propylene acetate, chloropropene, trimethyl-(3-propenylamine-3-dimethylpropyl)-ammonium chloride, acrylamide-2 -methylpropanesulfonic acid, vinyl vinyl carbonate, glycerol monopropenyl ether, and the like.

Further, the ethylene content of EVOH is a value determined at the time of polymerization of ethylene and vinyl ester, and is not a value which changes before and after saponification. The above ethylene content is a value measured based on ISO 14663, and is usually 20 to 60 mol%, preferably 20 to 55 mol%, more preferably 25 to 50 mol%. When the ethylene content is too small, the moldability at the time of melt molding tends to be lowered. On the other hand, when the ethylene content is too high, the gas barrier properties tend to be lowered when used in a molded article.

The average degree of saponification of the vinyl ester component in the above EVOH is a value measured based on JIS K6726 (however, measured in a solution state in which EVOH is uniformly dissolved in a water/methanol solvent), and is usually 90 to 100 mol%. It is preferably 95 to 100 mol%, more preferably 99 to 100 mol%. When the degree of saponification is too low, there is a tendency that gas barrier properties, moisture resistance, and the like are lowered.

Further, the melt flow rate (MFR) (210 ° C load 2160 g) in EVOH is usually 0.1 to 100 g/10 min, preferably 0.5 to 50 g/10 min, more preferably 1 to 30 g/10 min. When the melt flow rate is too low, the melt molding is in a high-torque state, and it tends to be difficult to form. If the melt flow rate is too high, the appearance properties or gas barrier properties of the molded article tend to be lowered. .

In the copolymerization of ethylene and vinyl ester, a known polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization is used, and among them, solution polymerization is preferably used. Further, as the solvent used in the solution polymerization, it is necessary to use a solvent which can dissolve ethylene, a vinyl ester, and an ethylene-vinyl ester copolymer of a polymerization product thereof, and an alcohol is usually used. The alcohol having 1 to 4 carbon atoms is preferable, and specific examples thereof include methanol, ethanol, n-propanol, isopropanol, and t-butanol. In addition, considering the saponification treatment described below, if the solvent used in the saponification treatment is the same as the solvent used in the above polymerization, the solvent substitution is not necessary, and the treatment such as recovery and reuse can be efficiently performed. The above polymerization solvent is particularly preferably methanol (MeOH).

The saponification of the ethylene-vinyl ester copolymer obtained by solution polymerization or the like is carried out by dissolving the copolymer in a solvent containing an alcohol such as an alcohol or water/alcohol, using a saponification catalyst. Further, the concentration of the ethylene-vinyl ester copolymer resin component in the alcohol-containing solution of the ethylene-vinyl ester copolymer is usually 20 to 70% by weight, preferably 30 to 60% by weight. The solvent is preferably an alcohol solvent. In the case of a water/alcohol mixed solvent, the mixing ratio (water/alcohol) is usually from (1/99) to (30/70), preferably (1/99). )~(20/80), more preferably (1/99)~(10/90).

Moreover, as a saponification catalyst, a base catalyst, an acid catalyst, etc. are mentioned. For example, specific examples of the alkali catalyst include alkali metal hydroxides such as sodium hydroxide or potassium hydroxide, and alkali metal alkoxides such as sodium methoxide, sodium ethoxide, potassium methoxide, or lithium methoxide. Examples of the acid catalyst include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, organic acids such as m-sulfonic acid, zeolites, and cation exchange resins. From the viewpoint of workability and industrial productivity, a base catalyst is preferred, and an alkali metal hydroxide is particularly preferred. The amount of use of the above-mentioned catalyst is appropriately selected depending on the target degree of saponification or the like. For example, in the case of using an alkali catalyst, it is usually 0.001 to 100 mmol equivalents, preferably 3 to 30 mmol equivalents, based on the amount of the fatty acid vinyl ester.

Regarding the method of saponification, any one of a batch type, a continuous type (belt type), or a tower type can be employed depending on the target degree of saponification. In view of the fact that the amount of the catalyst at the time of saponification can be reduced and the saponification reaction can be easily performed with high efficiency, a tower apparatus (not shown) is preferable.

Further, the saponification reaction is usually carried out while maintaining the system in a solution state in an alcohol solvent under heat and pressure, but the pressure can be adjusted by the ethylene content of the ethylene-vinyl ester copolymer. For example, specifically, the pressure is usually selected from the range of 0 to 1 MPaG, preferably from 0.1 to 0.5 MPaG, and the temperature is usually 50 to 180 ° C, preferably 80 to 160 ° C. Further, the saponification reaction time is usually from 0.1 to 6 hours. In addition, the "MPaG" unit is a unit of the gauge value, which indicates the difference between the absolute pressure and the atmospheric pressure (the same applies to "MPaG" below).

In addition, the EVOH after the saponification reaction is derived from the reaction system in the form of a solution of a high-temperature high-pressure alcohol solution or a water/alcohol solution or the like as a solvent, and is directly supplied to the storage tank or the like as needed, and then supplied to the above-mentioned preparation. Wash the washing step in the container. For example, specifically, S in FIG.

Further, in the saponification reaction, the vinyl ester portion of the ethylene-vinyl ester copolymer is converted into a hydroxyl group, and the carboxylic acid ester of the by-product is formed by leaving the group. For example, when vinyl acetate is used as the vinyl ester, methyl acetate (MeAc) is produced as a by-product of saponification.

Further, in the case where the saponification catalyst is an alkali catalyst, the metal of the catalyst will produce a by-product of the metal carboxylate. For example, when vinyl acetate is used as the above vinyl ester and sodium hydroxide is used as a catalyst, a by-product of sodium acetate is produced. Further, since the carboxylic acid is oxidized by the reductant or the alcohol, a by-product of the corresponding aldehyde is produced. For example, in the saponification of an ethylene-vinyl acetate copolymer, a by-product of acetaldehyde will be produced.

Next, a step of substituting a part of the alcohol in the solution containing the EVOH and the alcohol obtained in the above saponification treatment step with water to obtain an EVOH aqueous composition having a small alcohol content will be described.

The method for producing an ethylene-vinyl alcohol copolymer according to the present invention is a treatment in which an alcohol in an alcohol-containing solution of the above EVOH is substituted with water, a by-product produced by saponification, and a contact used in saponification. The residue of the medium is dissolved in water and removed. Furthermore, it is preferable to carry out the above-described processing in plural times. In the case of being divided into a plurality of times, in more detail, there is a main washing step after the preliminary washing step. At this time, a plurality of other washing steps may be performed between the preliminary washing step and the main washing step as needed.

<Description of the preliminary washing step>

First, in the washing container in the preliminary washing step, a washing container having a tower type container such as a perforated tray column or a bubble column or a packed column is used. In the above-mentioned layered tower method, the number of theoretical plates is usually 2 to 20 layers, preferably 5 to 15 layers. Moreover, the filling tower method also sets the amount of the filling accordingly. Introducing a solution containing EVOH and alcohol with water vapor and/or water into the column type vessel, and by contacting the two, replacing a part of the alcohol in the EVOH solution with water, and containing EVOH, alcohol, and water The glue, as well as the mixture of water and alcohol, is withdrawn from the tower vessel.

The introduction position of the solution containing EVOH and alcohol into the column type container, the introduction position of water vapor and/or water, and the extraction position of the alcohol- and water-containing glue of EVOH and the water/alcohol mixture can be arbitrarily set. The contact of the alcohol solution of the EVOH with water or water vapor may be either reverse flow or forward flow, but from the viewpoint of substitution efficiency, it is preferred to bring it in contact in a reverse flow. Specifically, it is preferable to introduce a solution containing EVOH and an alcohol from the upper portion of the column, introduce water vapor from the lower portion of the column, and bring the solution into a reverse flow contact with the solution, and the alcohol vapor and the steam are supplied together from the tower. The upper part is led out and the EVOH alcohol-containing and water-containing glue is discharged from the lower part of the tower.

Further, in the case of using a laminate column, the supply position of the solution containing EVOH and alcohol is usually 2 to 8 layers from the top of the column, preferably 2 to 4 layers. The reason is as follows: since the layer above the supply position is used to supply water or adjust the amount of water vapor to be introduced, and a water layer is formed on the shed, it is possible to prevent droplets such as EVOH from being mixed into the water and alcohol mixed vapor derived from the upper portion of the column. Medium and can prevent contamination in the steam delivery pipe or condenser.

Further, from the viewpoint of substitution efficiency, the supply position of the water vapor is usually at the bottom of the column, but it may be provided in the first to fifth layers above the bottom of the column as needed. Further, the mixed vapor of the alcohol and the water derived from the above-mentioned column can be liquefied by a condenser or the like, separated and purified, and reused.

Specifically, for example, as shown in Fig. 1, a solution containing EVOH and an alcohol obtained in the above saponification step is introduced from the slurry inlet 1a of the upper portion of the column using a column type washing container 1 having a plurality of layers 1d. The inside of the washing container 1 is introduced into contact with the water vapor introduced into the washing container 1 from the steam inlet 1s at the lower portion of the column, instead of a part of the alcohol in the solution, and the rubber containing EVOH, alcohol, and water is contained. The slurry is withdrawn from the rubber outlet 1b at the bottom of the column, and a part of the above-mentioned substituted alcohol is discharged together with water vapor from the exhaust port 1c at the top of the column to the outside of the container.

Further, at this time, in addition to the water (and/or water vapor) discharged from the exhaust port 1c, a part of the by-product of saponification is discharged together with the water, and the EVOH and the EVOH thereof can be reduced. The molded article has impurities such as color change.

The content of the alcohol and water in the dope containing EVOH, alcohol, and water derived from the above-described tower type container can be controlled by the following conditions: that is, water of the solution containing EVOH and alcohol introduced into the container (and / or the amount of water vapor introduced, and the temperature or pressure in the tower. The method for controlling the water described above cannot be generalized depending on the specifications of the column type container to be used, for example, the ratio of the cross-sectional area to the column length, the number of layers, or the pore size and number of the perforated plates. The conditions shown.

The concentration of the EVOH resin component introduced into the solution containing EVOH and alcohol in the preliminary washing step is usually 10 to 70% by weight, preferably 20 to 65% by weight, more preferably 30 to 60% by weight. Further, when the solvent is water/alcohol, the weight ratio of the mixing ratio (water/alcohol) is usually (1/99) to (80/20), preferably (1/99) to (70/). 30), more preferably (1/99) to (60/40), and usually contains 80 to 500 parts by weight, preferably 100 to 300 parts by weight, based on 100 parts by weight of the EVOH.

If the amount of introduction of water vapor (or water) introduced into the column type container is too small, the substitution efficiency with alcohol is insufficient; conversely, too much is disadvantageous for the cost side. The amount of the water vapor is usually 0.01 to 30 times by weight, preferably 0.1 to 10 times, more preferably 0.5 to 5 times, relative to the amount of introduction of the EVOH solution.

The temperature of the introduced water and steam is usually 30 to 200 ° C, preferably 80 to 180 ° C, more preferably 100 to 150 ° C. From the viewpoint of substitution efficiency, it is particularly preferable to introduce the water vapor into the container. The water and the water vapor may be obtained by purifying the mixed vapor of the alcohol and water derived from the container, or may be a mixed vapor containing a certain amount of alcohol. Further, in the case of a mixed vapor containing a certain amount of alcohol, the content of the alcohol is usually 10 parts by weight or less per 100 parts by weight of the water vapor, and from the viewpoint of the substitution efficiency of the water-alcohol, it is preferably an alcohol. Less in content, ideally for those who do not contain alcohol at all.

The temperature in the column type container is usually 80 to 200 ° C, preferably 100 to 180 ° C, more preferably 110 to 150 ° C. When the temperature is too low, the viscosity of the EVOH solution in the container becomes high, and the substitution efficiency may be lowered. Conversely, if the temperature is too high, the resin itself tends to deteriorate.

The pressure in the column type vessel is usually 0 to 1 MPaG, preferably 0 to 0.5 MPaG, more preferably 0.1 to 0.3 MPaG. When the pressure is too low, the substitution efficiency tends to decrease. When the pressure is too high, the temperature in the container rises and the EVOH tends to be thermally deteriorated.

Through the preliminary washing step, the dope containing EVOH, alcohol, and water derived from the column type container usually contains 10 to 200 parts by weight of the alcohol with respect to 100 parts by weight of the EVOH. The amount of the alcohol is preferably from 20 to 150 parts by weight, more preferably from 30 to 120 parts by weight, based on the entire amount of the glue. Further, the EVOH resin component in the dope is usually 20 to 60% by weight, preferably 30 to 50% by weight, and is usually 20 to 200 parts by weight, preferably 30 to 150 parts by weight, based on 100 parts by weight of the EVOH. More preferably, it is 40 to 100 parts by weight of water. The viscosity of the glue is a value of a viscosity of 500 g of a cement in a glass autoclave using a steel ball having a diameter of 3 mm and using a ball viscosity measurement method (Stoker type), and the value is usually 10 ¹ to 10 ⁵ mPa. s, preferably 10 ¹ to 10 ⁴ mPa ‧ , particularly preferably 10 ¹ to 10 ³ mPa, s. If the alcohol content is relatively small, the viscosity of the cement tends to increase.

Further, when the water/alcohol ratio at this time is expressed by the weight ratio of (water/alcohol), it is usually (1/99) to (80/20), preferably (10/90) to (75/25). More preferably (30/70)~(70/30). When the content of the above alcohol and water is too large, the burden of the main washing step tends to increase. Further, when the content of the alcohol and water is too small, the viscosity is high, and the substitution efficiency of the latter half of the column type container is lowered, or the derivation from the column type container tends to be difficult.

Further, the residual saponification catalyst contained in the dope is a acetate acetate in the case where the saponification catalyst is an alkali catalyst, and acetic acid in the case where the saponification catalyst is an acid catalyst. The content of the residual saponification catalyst is usually from 1,000 to 4,000 ppm, preferably from 1,500 to 3,000 ppm, more preferably from 1,700 to 2,700 ppm with respect to EVOH. Further, in the case of a base catalyst, the above content is obtained by extracting a base (metal) with a 1% by weight acetic acid solution and measuring by ion chromatography.

Further, if necessary, a well-known water/methanol adjustment step, a step of adding a known additive described below, or introduction of water into the EVOH may be performed between the preliminary washing step and the main washing step described below. Or water vapor) steps, etc. For example, it is preferred that the dope contains a heat stabilizer before the dope obtained in the preliminary washing step is supplied to the main washing step, and it is particularly preferable to contain acetic acid and boric acid. In the case of acetic acid, the amount thereof is usually 1,500 to 4,000 ppm with respect to EVOH; and in the case of boric acid, the amount thereof is usually 100 to 1000 ppm with respect to EVOH.

<Description of main cleaning steps>

Next, the main washing step of the characteristic steps of the present invention will be described.

The EVOH dope supplied to the main washing step (hereinafter, for convenience of explanation, the EVOH dope supplied to the main washing step is also referred to as EVOH dope (I)) is a rubber containing an ethylene-vinyl alcohol copolymer and an alcohol. Pulp. The alcohol content of the EVOH dope (I) is usually from 3 to 200 parts by weight, preferably from 5 to 150 parts by weight, more preferably from 10 to 120 parts by weight, based on 100 parts by weight of the EVOH. Further, the EVOH resin component is usually 10 to 60% by weight, preferably 10 to 50% by weight.

In the case where the dope contains water, the water content thereof is usually 20 to 1000 parts by weight, preferably 40 to 500 parts by weight, more preferably 40 to 300 parts by weight, based on 100 parts by weight of the EVOH. Further, when the water/alcohol ratio at this time is expressed by the weight ratio of (water/alcohol), it is usually (1/99) to (70/30), preferably (10/90) to (70/30). More preferably (30/70)~(70/30).

The viscosity of the EVOH cement is a value of a viscosity of 500 g of a cement in a glass autoclave using a steel ball having a diameter of 3 mm and using a ball viscosity measurement method (Stoker type), and the value is usually 10 ¹ to 10 ⁶ mPa. ‧ s, preferably 10 ² ~ 10 ⁶ mPa ‧ s, especially preferably 10 ² ~ 10 ⁴ mPa ‧ s.

Further, in the case where the EVOH dope (I) is a non-aqueous dope containing EVOH and an alcohol, it is preferred to adjust the viscosity by temperature or pressure, and supply it to the main washing step in the above-mentioned state of the dope.

Here, the EVOH dope (I) supplied to the main washing step is in a state in which a residual saponification catalyst is further contained, and the content of the residual saponification catalyst is usually from 1,000 to 4,000 ppm, preferably from 1,500 to 3,000 ppm, based on EVOH. More preferably, it is 1700~2700ppm. Further, in the case of a base catalyst, the above content is obtained by extracting a base (metal) with a 1% by weight acetic acid solution and measuring by ion chromatography.

The main washing step generally employs a horizontal washing tank having a glue introduction port, a glue outlet, a washing water introduction port, and a drain port at an arbitrary position. Specific examples of the shape of the horizontal washing tank include a rectangular parallelepiped shape and a cylindrical shape. The above-mentioned dope is conveyed in the longitudinal direction of this horizontal washing tank.

Further, the main washing step is to set the EVOH dope (I) [preferably EVOH dope (I) obtained by previously containing water in the preliminary washing step to lower the alcohol component] a slurry introduction port of the cleaning tank is introduced into the tank to be in contact with the washing water introduced into the tank from the washing water inlet of the horizontal washing tank, and a part of the alcohol remaining in the mortar or All of them are discharged from the separately provided drain port to the horizontal washing tank together with the washing water, and a cement-like EVOH aqueous composition having a lower alcohol content is obtained from the gel outlet port [hereinafter, for convenience of explanation, in the main washing The glue obtained in the net step is also called EVOH glue (II)].

Furthermore, the most characteristic feature of the present invention is that in the main washing step, a crucible device having a mortar built in a horizontal washing tank is subjected to surface renewal in the washing water. The surface and the inside of the above-mentioned EVOH and alcohol-containing dope [EVOH dope (I)] are repeatedly replaced and simultaneously kneaded so that the gel-like EVOH resin is not missing in the interior of the dope. Get in touch with the wash water. That is, hydrazine is carried out in the liquid phase.

The contact of the introduced dope with the washing water may be either reverse flow or forward flow, but from the viewpoint of substitution efficiency, it is preferred to bring it in contact with the reverse flow. The EVOH dope (I) may be supplied to the above-described washing tank continuously or intermittently, but from the viewpoint of production efficiency, continuous supply is preferred.

Further, the amount of dealcoholation per 100 parts by weight of the EVOH in the horizontal washing tank is usually 80 to 100% by weight based on the amount of the alcohol contained in the slurry before introduction into the horizontal washing tank. It is preferably from 90 to 100% by weight, particularly preferably from 96 to 100% by weight.

Specifically, for example, as shown in Fig. 1, the EVOH dope (I) is introduced into the horizontal washing tank 2 from the slurry introduction (input) port 2a at the upper portion of the tank, and is introduced into the washing water from the lower portion of the tank. The mouth 2w is introduced into the washing water in the horizontal washing tank 2, and a part or all of the alcohol remaining in the EVOH cement (I) is replaced with water, and is discharged together with the washing water from the drain port 2c at the upper portion of the tank. Outside the container. On the other hand, a cement-like EVOH aqueous composition [EVOH dope (II)] having a small alcohol content was obtained from the rubber discharge port 2b at the bottom of the tank.

The bath ratio of the above-mentioned horizontal washing tank is expressed by the weight ratio of the water to be introduced into the washing liquid, and the value is usually 0.5 to 10, preferably 0.6 to 5, more preferably 0.8 to 3. The above bath ratio affects the substitution efficiency of the alcohol, and when the bath ratio is too high, the economical tendency tends to be lowered. Further, when the bath ratio is too low, there is a tendency that the substitution and the cleaning efficiency are lowered.

Further, the residence time of the dope in the horizontal washing tank is changed according to the characteristics of the intended EVOH, but it is usually 0.5 to 10 hours, preferably 1 to 8 hours, more preferably 1 to 5 hours. .

The introduction amount of the EVOH dope (I) introduced into the washing tank is changed in accordance with the bath ratio, but the amount is usually 10 to 90% by volume/time, preferably 10 to 50, relative to the internal volume of the horizontal washing tank. The volume %/time is more preferably 10 to 25 vol%/time. If it is too small, there is a tendency that the substitution efficiency with alcohol is low. On the other hand, if there are too many, there is a tendency that the rate of derivation from the washing tank cannot catch up with the economy.

Further, the temperature of the introduced EVOH dope (I) is usually 40 to 110 ° C, preferably 50 to 100 ° C. Further, the residence time of the washing water is usually 0.5 to 20 hours, preferably 0.5 to 15 hours.

Further, it is preferable to keep the temperature in the washing tank constant. The temperature in the washing tank is usually 50 to 150 ° C, preferably 60 to 120 ° C, more preferably 70 to 110 ° C. In the case where the above temperature is too high, the viscosity of the glue becomes low, and in the case where the above temperature is too low, it may become difficult to handle due to an increase in viscosity. In particular, it is preferred to adjust the above temperature by washing water. This is to maintain the fluidity of the introduced glue. Therefore, considering the natural heat dissipation, the temperature of the washing water is usually 70 to 160 ° C, preferably 80 to 130 ° C.

Further, the main washing step in the present invention can be carried out under normal pressure conditions, but can also be carried out under varying pressure as needed. The above pressure is usually 0 to 1 MPaG, preferably 0 to 0.6 MPaG, more preferably 0 to 0.3 MPaG. When the pressure is too high, EVOH tends to be thermally deteriorated due to an increase in temperature in the container.

Further, it is preferred to add at least one heat stabilizer selected from the group consisting of a carboxylic acid, a carboxylate, a boron compound, and a phosphoric acid compound to the washing water introduced into the horizontal washing tank. With the enthalpy of the dope in the above-mentioned washing water, the heat stabilizer can be uniformly dispersed in the dope while being washed.

The carboxylic acid is preferably a carboxylic acid having 2 to 4 carbon atoms, and more preferably a monovalent or divalent carboxylic acid. Specifically, for example, oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, propionic acid, or lactic acid is used, and among these acids, acetic acid is preferably used in terms of cost and ease of availability. .

In the case where the above carboxylic acid is added, the content of the carboxylic acid in the obtained EVOH dope (II) after the main washing step is usually measured by titration to be 10 to 10000 ppm, preferably 50 with respect to EVOH. ~3000ppm, more preferably 100~2000ppm. If the content of the carboxylic acid is too small, the effect of containing a sufficient carboxylic acid may not be obtained. Conversely, if the content of the carboxylic acid is too large, it may be difficult to obtain a uniform film. Further, the concentration of the carboxylic acid in the cleaning liquid is usually from 10 to 3,000 ppm, preferably from 20 to 1,000 ppm, more preferably from 30 to 500 ppm.

Further, from the viewpoint of the balance effect of the heat stabilizer, a carboxylate is intentionally added, and the carboxylate is usually a carboxylate having 2 to 4 carbon atoms. Further, it is preferred to use a monovalent or divalent carboxylate. Specifically, for example, a salt such as an alkali metal salt (sodium or potassium) such as oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, propionic acid or lactic acid, or an alkaline earth metal salt (calcium or magnesium) is used. Among these salts, acetates, particularly sodium acetate, are preferred from the viewpoints of cost and ease of availability.

In the case where the above carboxylate is added, the content of the carboxylate in the obtained EVOH dope (II) after the main washing step is converted by the metal in the atomic absorption analysis, usually relative to the EVOH dope. 10 to 5000 ppm, preferably 30 to 1000 ppm, more preferably 50 to 700 ppm. Too little may cause color change during melt forming; too, if too much, the melt viscosity may become high. Further, the concentration of the carboxylate in the cleaning liquid is usually from 10 to 3,000 ppm, preferably from 20 to 1,000 ppm, more preferably from 30 to 500 ppm.

Examples of the boron compound include boric acid such as boric acid, boric acid ester, and borate, and boron hydride. Particularly, boric acid or borate is preferably used, but the compound is not limited thereto. Specific examples of the boric acid include orthoboric acid, meta-boric acid, and tetraboric acid; and examples of the boric acid ester include triethyl borate and trimethyl borate; and examples of the borate include various alkalis of the above boric acid. Metal salt, alkaline earth metal salt, or borax. Among these compounds, boric acid is preferred.

In the case where the above boron compound is added, the content of the boron compound in the obtained EVOH dope (II) after the main washing step is converted in terms of boron (after ashing, analysis by ICP emission analysis), usually relative The EVOH cement is 10 to 10000 ppm, preferably 100 to 8000 ppm, more preferably 100 to 7000 ppm. When the content of the boron compound is too small, the effect of improving the thermal stability is small, and if it is too large, it is a cause of gelation, and the moldability tends to be poor. Further, the concentration of the boron compound in the cleaning liquid is usually from 10 to 3,000 ppm, preferably from 20 to 1,000 ppm, more preferably from 30 to 500 ppm.

As the phosphoric acid compound, for example, various acids such as phosphoric acid and phosphorous acid, or a salt thereof, or the like can be used. The phosphate may be in the form of any of the first phosphate, the second phosphate or the third phosphate, and the type of the cation is not particularly limited, but an alkali metal salt or an alkaline earth metal salt is preferred. Further, it is preferred to add a phosphate compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate.

In the case where the above-mentioned phosphoric acid compound is added, the content of the phosphoric acid compound in the obtained EVOH dope (II) after the main washing step is converted to phosphate in the EVOH dope (analyzed by ion chromatography). Usually 1~1000ppm. By adding in the above range, it is possible to suppress the color change of the molded product and the generation of the glue or the fisheye. If the content is too small, the color tends to become prone to be formed during the melt molding. On the other hand, if too much, there are It is possible that the formed article is liable to produce glue or fish eyes. Further, the concentration of the phosphoric acid compound in the cleaning liquid is usually from 1 to 3,000 ppm, preferably from 10 to 1,000 ppm, more preferably from 20 to 500 ppm.

Next, the internal structure of the horizontal washing tank used in the main washing step described above will be described in detail.

The horizontal washing tank has a weir device that applies a shearing force to the above-mentioned dope, and examples thereof include a weir device having a screw, a gear, or a vane. The shearing force applied to the dope by these crucible means is preferably perpendicular to the longitudinal direction of the horizontal washing tank, in other words, it is preferably perpendicular to the flow direction of the dope. Further, as an accessory device, a temperature adjustment means such as a jacket or a coil or a screw shaft in which a heater is built is preferable. 2 is a longitudinal cross-sectional view (cutting mode) showing the internal structure of the horizontal washing tank 2 used in the main washing step of the embodiment; FIG. 3 is the inside of the horizontal washing tank 2 when viewed from the upper side. Sectional view.

The main structure of the horizontal washing tank in the present embodiment includes a substantially rectangular (box-shaped) groove body in which water can be stored in advance, and a screw for licking the above-mentioned dope. The above-mentioned screw may be one or a plurality of screws, but has a tendency to be excellent in cleaning efficiency at a plurality of times. Among them, in terms of operational efficiency, 2 to 5 are preferred, especially 2 are better. Specifically, as shown in FIG. 3, the main structure of the horizontal washing tank 2 in the present embodiment includes a substantially rectangular (box-shaped) groove body 2d in which water can be stored in advance; and a pair (2) The screws 2s and 2s ' are used to knead the above-mentioned dope, wherein the screw threads exert a shearing force in a direction perpendicular to the longitudinal direction of the horizontal washing tank.

In the present invention, the above-described tank system is horizontally disposed or inclined. In the case of the tilt setting, it is configured to be inclined by θ° with respect to the horizontal. This θ° is usually more than 0° to 45°, preferably 10° to 30°. Here, when the horizontal washing tank is inclined by θ° with respect to the horizontal direction (when θ°>0), it is preferable to set the inlet of the EVOH dope (I) to the upper side, and the washing is completed. The glue-like EVOH aqueous composition [EVOH glue (II)] is used to provide the glue outlet for the lower side, and it is preferable to set the washing water injection port to the lower side and to discharge the washing water. The outlet is placed on the upper side. By adjusting the set position in this way, the reverse flow contact between the glue and the washing water can be performed with high efficiency, and the cement with a heavier specific gravity can be discharged from the lower portion of the tank, and the recovery efficiency of the washed glue is improved. tendency.

Specifically, as shown in Fig. 2, the horizontal washing tank 2 in the present embodiment is inclined by 15° with respect to the horizontal. a glue introduction port 2a is provided on the upper end of the upper side (the left side of the drawing) which is inclined downward, which is an input port of the glue containing the mixture of EVOH and water/alcohol derived from the preliminary washing step; And at the other end of the lower side (right side of the figure), a glue outlet 2b is provided for deriving the EVOH aqueous composition [EVOH glue] which is finished in the tank body 2d. (II)]. Further, reference numeral 2w in Fig. 2 denotes a washing water introduction port, and 2c is a drain port for the washing water, and is configured such that the washing water can come into contact with the glue in a reverse flow. Moreover, the watertight structure is formed in the glue discharge port 2b, and only the glue can be taken out without leaking water (washing water).

The screw can be constructed of a shaft and a plurality of fins assembled on the shaft. Specifically, for example, the front ends of the respective fins are arranged in parallel along the longitudinal direction of the groove main body 2d, and the front ends of the respective fins are placed in close contact with each other to form a so-called "two-axis type" type crucible device. However, the two-axis type of boring device differs from the conventional boring machine in that a large gap (or space, gap) is provided between the screw and the groove body, which is a "large gap type". The screw is rotated in the water (washing water) filled in the gap, and a shearing force is applied to the glue to perform surface renewal, and the crucible in the liquid phase is used in the glue. Alcohol, impurities and the like are efficiently dissolved in the washing water.

Further, the above-mentioned "void" indicates the closest distance between the front end portion of the fin of the screw and the inner wall of the horizontal washing tank. The void is usually 1 to 20 mm, preferably 5 to 15 mm, more preferably 5 to 10 mm. In the case where the gap is too wide, the surface renewal efficiency of the cement tends to be low, and when it is too narrow, the efficiency of transporting the glue tends to be lowered. In addition, although a number of opportunities for contact with the washing water are reduced, a general downtime can also be used.

Further, in the present invention, it is preferable to adjust the arrangement of the screw so that the surface and the inside of the paste containing EVOH and water/alcohol can be repeatedly replaced to perform surface renewal. For example, the direction of rotation of the screw can be adjusted so that it becomes the direction in which the screw is engaged.

For example, in the present embodiment, in the case of two screws, the jaw type apparatus is designed such that the two screws 2s and 2s ' are respectively oriented in different directions as shown in Fig. 3 (in this example) Both are inwardly engaged in the direction of rotation. Further, since the groove main body 2d is filled with water, the portion (bearing or the like) that supports the shaft of the screw is a watertight and waterproof structure. Further, each of the screws is connected to a rotary power source such as a motor (not shown).

In addition, the fins (vanes) assembled on the shaft have, for example, eye-catching flat vanes (Pf), helical vanes (Ph) that are reinforced in the crucible, or reversed transport materials. A spiral vane (Pr) or the like is used in combination with a screw portion (Ps) that conveys (feeds) the material to the downstream side. As shown in Fig. 3, the combination of the vanes in the present embodiment combines a screw portion (Ps), a spiral vane (Ph), and a reverse spiral vane (Pr), but the combination may be in accordance with the glue. The viscosity is appropriately changed.

Further, as a condition of the crucible device which can be used in the present embodiment, in order to apply shear to the dope, it is necessary to have a decomposition and crushing function while stirring and twisting. Therefore, in the case where the supplied glue is continuously washed, a double-wrap type, a cokneader type, or a scraper may be used in addition to the above-described two-axis type. Votator type equal device. Further, a mixer such as a ribbon type, a screw type, a vane type, a muller type, or a radiation rod type, a needle mixer, a cutter agitator, a rod mixer, or an internal mixer, or a ball may be used. A horizontal uniaxial or multi-axis boring device such as a grinder such as a rod-shaped grinder or a pug mill. In the present invention, a continuous treatment or a batch treatment may be employed, but from the viewpoint of production efficiency, a continuous treatment type is preferred.

For example, specifically, in the cleaning liquid, the advancement action of the screw portion of each screw (2s and 2s ' ) and/or the inclination of the bottom surface of the horizontal cleaning tank 2 are performed, so that the glue introduction port from the upstream side is used. 2a smoothly conveys the glue introduced into the horizontal washing tank 2 toward the slurry outlet 2b on the downstream side, and at the same time, the glue is produced by the shearing action generated between the opposing vanes and between the screw portions. The outside of the slurry enters the inside, and the crucible is so that the inside of the dope is renewed to the outside, and the surface of the dope is sequentially updated, in other words, by thorough contact with the above-mentioned washing water by rubbing in the liquid phase.

Therefore, in the dope containing the ethylene-vinyl alcohol copolymer and the alcohol in the present embodiment, at the same time as the above-mentioned washing water, some or all of the alcohol and the catalyst residue and by-products used in the saponification are efficiently efficiently. Remove. Further, since at least one additive selected from a carboxylic acid, a carboxylate, a boron compound, and a phosphoric acid compound is added as a heat stabilizer to the washing water, the additive can be uniformly dispersed along with the enthalpy of the above-mentioned dope. Mixed in the glue.

In the EVOH aqueous composition [EVOH cement (II)] obtained in the main washing step of the present invention, the EVOH resin component is usually 30 to 80% by weight, preferably 40 to 70% by weight; The amount of water is usually 30 to 400 parts by weight, preferably 40 to 240 parts by weight, more preferably 50 to 150 parts by weight, per 100 parts by weight of the EVOH. Further, the alcohol may be contained in an amount which is not completely removed, but the content thereof is usually less than 10 parts by weight, preferably less than 5 parts by weight, more preferably less than 3 parts by weight, based on 100 parts by weight of EVOH. In general, it is preferred to monitor the content of the alcohol in the aqueous EVOH composition in the above-mentioned horizontal washing tank 2 as the end point at which the desired alcohol concentration is reached.

The viscosity of the above-mentioned EVOH paste 500 g was measured by a ball of 3 mm in a glass autoclave using a ball of a diameter of 3 mm, and the measured value was usually 10 ¹ to 10 ⁶ mPa·s, preferably 10 ³ ~ 10 ⁶ mPa‧s, especially 5 × 10 ⁴ ~ 10 ⁶ mPa‧s. The less the alcohol content becomes, the more the viscosity of the glue tends to rise.

Further, since the residual saponification catalyst contained in the obtained EVOH dope (II) is washed in the main washing step, the content of the residual saponification catalyst is usually 0 to 3000 ppm with respect to EVOH, preferably It is 0 to 2000 ppm, more preferably 0 to 1000 ppm. Further, the above content is obtained by calculating the acetate in the case of an alkali catalyst.

Further, in the washing step of the present embodiment, in the preliminary washing step using the column type washing container, the alcohol is not completely removed, and the state in which the fluidity is retained is retained, thereby preventing the treatment efficiency from being lowered. Therefore, in the main washing step using the horizontal washing tank, by forcibly stirring and rubbing it, it is brought into contact with the washing water, and high efficiency can be performed even if the mortar becomes high in concentration and high in viscosity. As a result of the substitution of the alcohol and water, as a result, the EVOH which is swollen by the inclusion of the alcohol shrinks simultaneously with the decrease in the alcohol content, and the alcohol is discharged from the paste together with water or the catalyst residue and by-products used in the saponification. A high-purity, high-quality EVOH aqueous composition is obtained (water content: 30 to 400 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of EVOH).

That is, the low-alcohol content EVOH aqueous composition [EVOH dope (II)] obtained in the present invention is to be obtained only in the column type washing container 1 of the preliminary washing step, since the container 1 is washed. The viscosity of the EVOH dope in the latter half of the treatment becomes too high, the fluidity is lowered, and the substitution efficiency of the alcohol-water is lowered, and it becomes impossible to be derived from the washing container 1, and thus it is difficult to obtain.

Further, in the horizontal washing tank 2 of the main washing step, if most of the alcohol in the alcohol solution of the EVOH is to be replaced with water, the initial solution viscosity introduced into the horizontal washing tank 2 is low, so that the introduction is performed. The washing water cannot stay in the EVOH cement for a long time, and thus there is a tendency to replace the low efficiency, time consuming, and requiring a large amount of water. Therefore, in the present invention, the step of substituting the alcohol in the solution containing EVOH and alcohol with water is preferably carried out in multiple stages in a preliminary washing step or the like.

Next, a step of drying the emulsified EVOH aqueous composition [EVOH dope (II)] having a small alcohol content obtained in the main washing step and granules (finished particles) will be described.

The granulation step may be exemplified by: (A) a method in which the aqueous EVOH-containing aqueous composition [EVOH (II) having a small alcohol content is formed into a particle shape in a state of water content, and then the moisture content is lowered; B) A method in which the moisture content of the EVOH aqueous composition [EVOH dope (II)] having a small alcohol content is lowered and then formed into a pellet shape.

As the method (A), for example, a cemented EVOH aqueous composition [EVOH dope (II)] having a small alcohol content is extruded through a pore, and is cut in a fluid state to obtain a circular shape. a method of granules (for example, hot cutting or water cutting, etc.); or extruding and solidifying EVOH dope (II) in a strip in a lower temperature refrigerant bath than the aqueous resin, and cutting the above-mentioned strip resin to obtain a cylinder Method of granules. Next, the obtained granules are dried by various well-known drying methods.

As the method (B), for example, a moisture content in a cement-like EVOH aqueous composition [EVOH dope (II) having a small alcohol content is reduced to a weight of EVOH 100 by using a centrifuge or an extruder in advance. The portion is usually 1 to 50 parts by weight, preferably 1 to 40 parts by weight, more preferably 1 to 30 parts by weight, and then granulated by an extruder or the like. In the granulation, a method in which an EVOH resin is extruded in a strip shape by an extruder and cut to obtain a columnar particle is exemplified, or a resin in a molten state at the time of extrusion from an extruder is obtained to obtain a circle. Shaped particles (thermal cutting), etc. In particular, in consideration of the thermal efficiency of the drying step or the heat history of the resin, in the case where an extruder is used, since the moisture of the EVOH aqueous composition can be lowered and a series of granulation operations are performed, it is preferably used. (B) Method.

As the extruder used in the above granulation step, a single-axis extruder or a twin-screw extruder can be cited. The diameter (mmφ) of the above extruder is usually 40 to 180, preferably 60 to 140, more preferably 70 to 110. Further, the L/D of the above extruder is usually from 10 to 80, preferably from 15 to 70, more preferably from 15 to 60. If the above L/D is too small, the dehydration effect is insufficient and the discharge tends to be unstable. Conversely, if the L/D is too large, excessive shearing tends to occur. Among them, a twin-screw extruder in which the direction of rotation of the screw is the same direction is preferable, and this is sufficient due to its moderate shearing.

At this time, the temperature of the resin in the extruder is usually 80 to 250 ° C, preferably 90 to 240 ° C, more preferably 100 to 230 ° C. When the temperature is too high, the resin tends to deteriorate the color change, and when it is too low, the water reduction efficiency tends to decrease. The method of adjusting the resin temperature is not particularly limited, and a method of appropriately setting the temperature of the cylinder in the extruder is generally used.

The number of screw rotations of the extruder is set according to the size of the shaft, and is usually in the range of 10 to 1000 rpm, preferably 30 to 800 rpm, more preferably 50 to 400 rpm. If the number of rotations is too small, there is a tendency that the discharge is unstable; and if it is too large, the resin may be deteriorated due to the heat generated by the shearing.

Specifically, for example, as shown in FIG. 1, the first extruder 3, the second extruder 4, and a slitter (granulator, not shown) are formed, and the main washing step is performed. The obtained cement-like EVOH aqueous composition [EVOH dope (II)] is sequentially introduced into the first extruder 3 and the second extruder 4 to be melted, and the moisture in the aqueous composition of the EVOH is slow. After the strip shape or the ribbon-shaped EVOH composition discharged from the second extruder 4 is cooled down, the EVOH composition is cut into a desired size by a slitter or the like to obtain a low alcohol. Low water content EVOH particles (EVOH-granules).

As the first extruder 3 and the second extruder 4 used in the granulation step, a general uniaxial extruder or a twin-screw extruder or the like can be used. A biaxial extruder is preferred because it can be sufficiently flawed by moderate shearing.

Further, the resin temperature in the extruder is usually set to 80 to 250 ° C, and the moisture content of the EVOH composition discharged from the first extruder 3 is usually adjusted to be 30 to 35 parts by weight with respect to the EVOH 100 weight portion. On the other hand, the moisture content of the EVOH composition discharged from the second extruder 4 is usually adjusted to be less than 10 parts by weight, preferably 0 to 8 parts by weight, per 100 parts by weight of the EVOH. Further, in the above granulation step, in order to minimize the water content of the EVOH composition, the resin temperature in the above extruder is usually set in the range of 120 to 250 ° C, preferably 150 to 230 ° C. . On the other hand, in order to suppress the thermal deterioration of the EVOH composition as much as possible, in order to maintain the water content, the resin temperature in the above extruder is usually set to 80 to 105 ° C, preferably 85 to 100 ° C, More preferably, it is carried out in the range of 90 to 100 °C.

Further, in the extrusion using the above extruder, in order to melt the EVOH composition [EVOH dope (II)] in a water-containing state, it is preferred to carry water or water from at least one place of the extruder. The vapor is discharged. The moisture discharge means at this time is not particularly limited, and a method of discharging from a dewatering hole, an air outlet, or a dewatering slit provided in a cylinder (cylinder) of the extruder may be employed. Among them, the dewatering slit is preferred because it can discharge either water or water vapor, so that the resin adheres or leaks less. Further, the above-described water discharge means may be plural types, and when a plurality of types are used, the same type or different types may be used in combination.

Moreover, the method of granulating the EVOH composition discharged from the second extruder 4 is not particularly limited, but it is preferable to use the EVOH composition in a strip shape from a press die (extrusion port) of the extruder. A method of cutting into an appropriate length after extrusion, cooling, and cooling. As a method of cooling the strip to be discharged, a method of bringing it into contact with a liquid which is kept at a temperature lower than the temperature of the extruded resin, or a method of spraying cold air, or the like is used.

In addition, the shape of the cut pellets is generally cylindrical, and the size of the stamper is preferably 2 to 6 mmφ from the viewpoint of convenience in the case of being used as a molding material. The cutting length is about 1~6mm. Further, it is preferred to use a method in which the EVOH composition discharged from the extruder is still in a molten state and cut in the atmosphere or in water.

Further, in the granulation step, two or more kinds of EVOH compositions different in polymerization degree, ethylene content, saponification degree, and the like obtained by different processes of the EVOH aqueous composition [EVOH dope (II)] may be mixed. , melt forming. In addition, various other plasticizers, slip agents, stabilizers, surfactants, colorants, ultraviolet absorbers, antistatic agents, desiccants, bridging agents, metal salts, fillers, and various reinforcing agents such as various fibers may be added in an appropriate amount. Etc., melting enthalpy.

Next, a particle drying step (not shown) for reducing the moisture content of the EVOH particles obtained in the above granulation step as needed will be described.

When the EVOH pellets obtained in the above granulation step are sufficiently removed from the water in the extruder and the moisture content is less than 0.3 parts by weight with respect to 100 parts by weight of the EVOH, the EVOH pellets can be used as a finished product in this state. Further, when the moisture removal is insufficient, the excess moisture is removed by the particle drying step.

As the drying method of the above EVOH pellets, a known drying method can be employed. For example, a static drying method, a flow drying method, etc. are mentioned specifically. Further, a multi-stage drying method by a different drying method can also be employed. In particular, a method of drying by a flow drying method in the first stage and drying by a static drying method in the second stage is preferred because it can make the color of the particles and the molded article using the particles good. Further, at the time of drying, it is preferred to circulate an inert gas such as nitrogen (N ₂ gas) therein because it makes the color tone of the molded article good.

For example, in particular, it is possible to circulate in a drying vessel by supplying an inert gas such as nitrogen (N ₂ gas) as needed, so that the volatile component content of the EVOH particles obtained in the above granulation step is lowered to the final product level. It is less than 0.3 parts by weight with respect to the EVOH 100 weight portion. Further, the volatile component was calculated by weight (including alcohol) which dried the pellet at 150 ° C for 5 hours.

According to the method for producing an ethylene-vinyl alcohol copolymer of the present invention, since the residence time required for the drying step is short, the obtained EVOH (particles) is not thermally deteriorated, and the quality of the EVOH and the molded article using the EVOH is improved. .

Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples without departing from the spirit thereof. In addition, in the example, "part" and "%" indicate the weight basis unless otherwise specified.

Example 1 [EVOH in methanol solution]

Into a polymerization vessel having a cooling coil, 330 parts by weight of vinyl acetate, 60 parts by weight of methanol, and 500 ppm of ethylene peroxide (relative to vinyl acetate) were injected, and once the system was replaced with nitrogen, ethylene was then substituted to introduce ethylene. The ethylene pressure was 3.6 MPa. Thereafter, the temperature was raised to 68 ° C while stirring, and polymerization was carried out for 6 hours until the polymerization ratio of vinyl acetate was 50% by weight. Thereafter, the polymerization reaction was stopped to obtain a methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 29 mol% (the concentration of the resin component was 48% by weight).

<Saponification step>

The residual vinyl acetate in the reaction solution was removed, and the methanol solution of the ethylene-vinyl acetate copolymer (concentration of the resin component: 48% by weight) was supplied from the upper portion of the tower of the layer column at a rate of 30 parts by weight per hour. At the same time, 0.54 parts by weight/hour of a sodium hydroxide methanol solution having a molar amount of 6 mmoles relative to the acetic acid group in the copolymer was supplied from the upper portion of the column. On the other hand, methanol was supplied from the lower portion of the tower at 60 parts by weight/hour. The temperature inside the tower is 120~140 °C, and the tower pressure is 0.36 MPaG. After 0.5 hours from the start of the injection, a methanol solution of EVOH was obtained. The EVOH has an ethylene content of 29 mol% and a degree of saponification of 99.5 mol%, and contains sodium acetate equivalent to the sodium component of the saponified catalyst sodium hydroxide in the solution. In addition, the unit of the "MPaG" unit gauge value indicates the difference between the absolute pressure and the atmospheric pressure.

<Preparation washing step>

Next, the methanol solution of the above EVOH was supplied to a tower type washing container (a 10-layer layered tower). The second layer of the laminate was counted at the top of the above-mentioned column type washing container, and 80 parts by weight/hour of a methanol solution of EVOH having a resin component concentration of 51% by weight was continuously supplied. On the other hand, 60 parts by weight of water vapor at 130 ° C was continuously supplied from the lowermost laminate, and the methanol solution of EVOH and water vapor were brought into reverse flow contact in the laminate column. The temperature in the tower type washing container was 120 ° C, and the pressure inside the vessel was 0.2 MPaG.

Further, from the slurry outlet port at the bottom of the column type washing container, a dope containing 75 parts by weight of methanol, 75 parts by weight of water, and 75 parts by weight of water was obtained [water/methanol (weight ratio) = 50). /50]. The EVOH resin component of the entire paste was 40% by weight. Further, the obtained dope contained 4,700 ppm of sodium acetate.

A water/alcohol solvent solution containing boric acid and acetic acid was added to the above EVOH dope, and the moisture adjustment of the dope was carried out.

<Main washing step>

The components and the EVOH cement of the following properties were supplied to the horizontal washing tank 2 described in the embodiment, and washed under the following conditions.

(EVOH glue)

The EVOH dope contains 141 parts by weight of methanol and 247 parts by weight of water [water/methanol (weight ratio) = 64/36] with respect to the weight portion of the EVOH 100, and the resin component thereof is 21% by weight, and contains the component relative to the EVOH resin. It is 2100 ppm of acetic acid, 7900 ppm of sodium acetate, and 4300 ppm of boric acid. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 80 ° C by a normal pressure drop ball viscosity measurement method (Stoker method), and the obtained value was 7000 mPa ‧ s.

A) Washing (搓揉, stirring) conditions

‧ Screw rotation number: 60 rpm

‧The gap between the screw and the inner wall of the groove: 8mm

‧In-tank temperature (expressed as water temperature before discharge): 79°C

B) EVOH glue conditions

‧Introduction: 17 parts/hour

‧Introduction of glue temperature: 80 ° C

‧ glue retention time: 3 hours

‧Exported amount: 6.4 parts/hour

C) Washing water conditions

Washing water composition (relative to water):

Acetic acid 160ppm

Sodium acetate 200ppm

Boric acid 110ppm

Sodium dihydrogen phosphate 80ppm

Calcium phosphate 150ppm

‧Introduction: 16 parts/hour

‧ Temperature: 85 ° C

Further, the bath ratio (wash water weight/EVOH cement weight ratio) was adjusted to 0.94.

Further, an EVOH dope of a white turbid high-viscosity cement was obtained from the rubber discharge port 2b of the above-mentioned horizontal washing tank 2. Further, the obtained EVOH dope contained 83 parts by weight of water and 2 parts by weight of methanol with respect to EVOH 100 parts by weight, and the resin component of EVOH was 49% by weight, and contained 1,360 ppm of acetic acid, 530 ppm of sodium acetate, 730 ppm of boric acid, and phosphoric acid with respect to the EVOH resin component. Sodium dihydrogen 80 ppm and calcium phosphate 150 ppm. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 120 ° C by a ball drop viscosity measurement method (Stoker method), and the obtained value was 80,000 mPa ‧ s.

That is, the amount of dealcoholization per 100 parts of EVOH of the dope in the horizontal washing tank was 99% by weight of the amount of the alcohol contained in the dope before introduction into the horizontal washing tank. The EVOH cement was molded into a sheet shape at normal temperature, cut into a narrow strip shape, and dried to obtain EVOH pellets. The MFR (210 ° C, load 2160 g) of the pellet was 3.0 g/10 min.

Example 2 [EVOH in methanol solution]

Into a polymerization vessel having a cooling coil, 330 parts by weight of vinyl acetate, 55 parts by weight of methanol, and 300 ppm of ethylene peroxide (relative to vinyl acetate) were injected, and once the system was replaced with nitrogen, ethylene was then substituted to introduce ethylene into The ethylene pressure was 3.3 MPa. Thereafter, the temperature was raised to 68 ° C while stirring, and polymerization was carried out for 6 hours until the polymerization ratio of vinyl acetate was 60% by weight. Thereafter, the polymerization reaction was stopped to obtain a methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 29 mol% (concentration of the resin component was 56% by weight).

<Saponification step>

The residual vinyl acetate in the reaction solution was removed, and the methanol solution of the ethylene-vinyl acetate copolymer (concentration of the resin component: 56% by weight) was supplied at a rate of 31 parts by weight per hour from the upper portion of the column tower. At the same time, 0.94 parts by weight/hour of a sodium hydroxide methanol solution having a molar amount of 6 mmoles relative to the acetic acid group in the copolymer was supplied from the upper portion of the column. On the other hand, methanol was supplied from the lower portion of the tower at 52 parts by weight/hour. The temperature inside the tower is 120~140 °C, and the tower pressure is 0.36 MPaG. After 0.5 hours from the start of the injection, a methanol solution of EVOH was obtained. The EVOH has an ethylene content of 29 mol% and a degree of saponification of 99.5 mol%, and contains sodium acetate equivalent to the sodium component of the saponified catalyst sodium hydroxide in the solution. In addition, the unit of the "MPaG" unit gauge value indicates the difference between the absolute pressure and the atmospheric pressure.

<Preparation washing step>

Next, the methanol solution of the above EVOH was supplied to a tower type washing container (a 10-layer layered tower). The second layer of the laminate was counted at the top of the column type washing container, and a methanol solution of EVOH having a concentration of 56% by weight of the resin component was continuously supplied in an amount of 52 parts per hour. On the other hand, 14 parts by weight of water vapor at 130 ° C was continuously supplied from the lowermost laminate, and the methanol solution of EVOH and water vapor were brought into reverse flow contact in the laminate column. The temperature in the tower type washing container was 120 ° C, and the pressure inside the vessel was 0.26 MPaG.

Further, from the slurry outlet port at the bottom of the column type washing container, a dope containing 100 parts by weight of EVOH, 100 parts by weight of methanol, and 50 parts by weight of water was obtained [water/methanol (weight ratio) = 33). /66]. The EVOH resin component of the entire paste was 40% by weight. Further, the obtained dope contained 5000 ppm of sodium acetate.

An aqueous solution containing boric acid and acetic acid was added to the above EVOH dope, and the moisture adjustment of the dope was carried out.

<Main washing step>

The components and the EVOH cement of the following properties were supplied to the horizontal washing tank 2 described in the embodiment, and washed under the following conditions.

(EVOH glue)

The EVOH dope contains 100 parts by weight of methanol and 75 parts by weight of water [water/methanol (weight ratio) = 43/57] with respect to the weight portion of the EVOH 100, and has a resin component of 36% by weight, and contains a component relative to the EVOH resin. It is 2100 ppm of acetic acid, 7900 ppm of sodium acetate, and 4300 ppm of boric acid. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 80 ° C by a normal pressure drop ball viscosity measurement method (Stoker method), and the obtained value was 8000 mPa·s.

A) Washing (搓揉, stirring) conditions

‧ Screw rotation number: 60 rpm

‧The gap between the screw and the inner wall of the groove: 8mm

‧In-tank temperature (expressed as water temperature before discharge): 79°C

B) EVOH glue conditions

‧Introduction: 17 parts/hour

‧Introduction of glue temperature: 80 ° C

‧ glue retention time: 3 hours

‧Exported amount: 6.4 parts/hour

C) Washing water conditions

Washing water composition (relative to water):

Acetic acid 150ppm

Sodium acetate 140ppm

Boric acid 30ppm

Sodium dihydrogen phosphate 130ppm

Calcium phosphate 150ppm

‧Introduction: 34 parts/hour

‧ Temperature: 85 ° C

Further, the bath ratio (washing water weight/EVOH cement weight ratio) was adjusted to 2 below.

Further, an EVOH dope of a white turbid high-viscosity cement was obtained from the rubber discharge port 2b of the above-mentioned horizontal washing tank 2. Further, the obtained EVOH dope contained 83 parts by weight of water and 2 parts by weight of methanol with respect to EVOH 100 parts by weight, and the resin component of EVOH was 54% by weight, and contained 1,360 ppm of acetic acid, 530 ppm of sodium acetate, 550 ppm of boric acid, and phosphoric acid with respect to the EVOH resin component. Sodium dihydrogen 80 ppm and calcium phosphate 150 ppm. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 120 ° C by a ball drop viscosity measurement method (Stoker method), and the obtained value was 88,000 mPa ‧ s.

That is, the amount of dealcoholization per 100 parts of EVOH of the dope in the horizontal washing tank was 99% by weight of the amount of the alcohol contained in the dope before introduction into the horizontal washing tank. The EVOH cement was molded into a sheet shape at normal temperature, cut into a narrow strip shape, and dried to obtain EVOH pellets. The MFR (210 ° C, load 2160 g) of the pellet was 3.4 g/10 min.

Example 3 [EVOH in methanol solution]

Into a polymerization vessel having a cooling coil, 400 parts by weight of vinyl acetate, 80 parts by weight of methanol, and 390 ppm of ethylene peroxide (relative to vinyl acetate) were injected, and once the system was replaced with nitrogen, ethylene was then substituted to introduce ethylene into The ethylene pressure was 3.6 MPa. Thereafter, the mixture was heated to 67 ° C while stirring, and polymerization was carried out for 6 hours until the polymerization ratio of vinyl acetate was 60% by weight. Thereafter, the polymerization reaction was stopped to obtain a methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% (concentration of the resin component was 53% by weight).

<Saponification step>

The residual vinyl acetate in the reaction solution was removed, and the methanol solution of the ethylene-vinyl acetate copolymer (concentration of the resin component: 53% by weight) was supplied from the upper portion of the tower column at a rate of 32 parts by weight per hour. At the same time, 1 part by weight/hour of a sodium hydroxide methanol solution having a molar amount of 8 mmoles relative to the acetic acid group in the copolymer was supplied from the upper portion of the column. On the other hand, methanol was supplied from the lower portion of the tower at 50 parts by weight/hour. The temperature inside the column is 100~120 °C, and the column pressure is 0.3 MPaG. After 0.5 hours from the start of the injection, a methanol solution of EVOH was obtained. The EVOH had an ethylene content of 32 mol% and a degree of saponification of 99.6 mol%, and contained sodium acetate equivalent to the sodium component of the saponified catalyst sodium hydroxide in the solution. In addition, the unit of the "MPaG" unit gauge value indicates the difference between the absolute pressure and the atmospheric pressure.

<Preparation washing step>

Next, the methanol solution of the above EVOH was supplied to a tower type washing container (a 10-layer layered tower). The second layer of the laminate was counted at the top of the above-mentioned column type washing container, and 80 parts by weight/hour of a methanol solution of EVOH having a concentration of the resin component of 53% by weight was continuously supplied. On the other hand, 6 parts by weight of water vapor at 130 ° C was continuously supplied from the lowermost laminate, and the methanol solution of EVOH and water vapor were brought into reverse flow contact in the laminate column. The temperature in the column type washing container was 111 ° C, and the pressure inside the vessel was 0.2 MPaG.

Next, from the slurry outlet port at the bottom of the column type washing container, a dope containing 117 parts by weight of EVOH, 117 parts by weight of methanol, and 61 parts by weight of water was obtained [water/methanol (weight ratio) = 34/ 66]. The EVOH resin component of the entire paste was 36% by weight. Further, the obtained dope contained 4000 ppm of sodium acetate.

An aqueous solution containing boric acid and acetic acid was added to the above EVOH dope, and the moisture adjustment of the dope was carried out.

<Main washing step>

The components and the EVOH cement of the following properties were supplied to the horizontal washing tank 2 described in the embodiment, and washed under the following conditions.

(EVOH glue)

The EVOH dope contains 117 parts by weight of methanol and 96 parts by weight of water [water/methanol (weight ratio) = 45/55] with respect to the weight portion of the EVOH 100, and has a resin component of 32% by weight, and contains a component relative to the EVOH resin. It is 1600 ppm of acetic acid, 1700 ppm of sodium acetate, and 180 ppm of boric acid. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 80 ° C by a normal pressure drop ball viscosity measurement method (Stoker method), and the obtained value was 7000 mPa ‧ s.

A) Washing (搓揉, stirring) conditions

‧ Screw rotation number: 60 rpm

‧The gap between the screw and the inner wall of the groove: 8mm

‧In-tank temperature (expressed by water temperature before discharge): 100°C

B) EVOH glue conditions

‧Introduction: 11 parts/hour

‧Introduction of glue temperature: 80 ° C

‧ glue retention time: 1.5 hours

‧Exported amount: 6.5 parts/hour

C) Washing water conditions

Washing water composition (relative to water):

Acetic acid 350ppm

Sodium acetate 370ppm

Boric acid 40ppm

Calcium phosphate 15ppm

‧Introduction: 23 parts/hour

‧ Temperature: 100 ° C

Further, the bath ratio (washing water weight/EVOH cement weight ratio) was adjusted to 2 below.

Next, an EVOH dope of a white turbid high-viscosity cement was obtained from the rubber discharge port 2b of the above-described horizontal washing tank 2. Further, the obtained EVOH dope contained 80 parts by weight of water and 1 part by weight of methanol with respect to EVOH 100 parts by weight, and the resin component of EVOH was 55% by weight, and contained 2,500 ppm of acetic acid, 630 ppm of sodium acetate, 660 ppm of boric acid, and phosphoric acid with respect to the EVOH resin component. Calcium 10ppm. Further, a steel ball having a diameter of 3 mm was used in a glass autoclave, and the viscosity of the paste 500 g was measured at 120 ° C by a ball drop viscosity measurement method (Stoker method), and the obtained value was 85,000 mPa·s.

That is, the amount of dealcoholization per 100 parts of EVOH of the dope in the horizontal washing tank was 99% by weight of the amount of the alcohol contained in the dope before introduction into the horizontal washing tank. The EVOH cement was molded into a sheet shape at normal temperature, cut into a narrow strip shape, and dried to obtain EVOH pellets. The MFR (210 ° C, load 2160 g) of the pellet was 4.8 g/10 min.

From the above results, some or all of the residual methanol may cause impurities such as EVOH and molded articles using EVOH, such as discoloration (residual catalysts and by-products at the time of saponification), and washing with the main washing step. The purified water is removed together with high efficiency.

The specific embodiments of the present invention have been shown in the above embodiments, but the above embodiments are merely illustrative and are not to be construed as limiting. Further, variations that are within the scope of the claims are all within the scope of the invention.

(industrial use possibility)

According to the method for producing an ethylene-vinyl alcohol copolymer of the present invention, impurities in the obtained EVOH product are reduced, and the quality of the EVOH and the molded article using EVOH is improved. In addition, the obtained EVOH pellets are melt-molded by extrusion molding, injection molding, or the like, and are molded into a molded article such as a film, a sheet, a cup, or a bottle, and are widely used in packaging of foods, pharmaceuticals, industrial chemicals, and agricultural chemicals. Use.

1. . . Washing container

1a. . . Glue inlet

1b. . . Glue outlet

1c. . . exhaust vent

1d. . . Laminate

1s. . . Water vapor inlet

2. . . Horizontal cleaning tank

2a. . . Glue inlet

2b. . . Glue outlet

2c. . . Drainage port

2d. . . Slot body

2s, 2s ' . . . Screw

2w. . . Washing water inlet

3. . . Extruder

4. . . Extruder

Ps. . . Screw section

Ph. . . Spiral vane

Pr. . . Inverse spiral vane

Fig. 1 is a flow chart showing an outline of an aspect of a method for producing an ethylene-vinyl alcohol copolymer of the present invention.

Fig. 2 is a longitudinal cross-sectional view showing the internal structure of a horizontal washing tank used in the main washing step of the embodiment of the present invention.

Fig. 3 is a cross-sectional view of the inside of the horizontal washing tank used in the main washing step of the embodiment of the present invention as viewed from the upper side.

1. . . Washing container

1a. . . Glue inlet

1b. . . Glue outlet

1c. . . exhaust vent

1d. . . Laminate

1s. . . Water vapor inlet

2. . . Horizontal cleaning tank

2a. . . Glue inlet

2b. . . Glue outlet

2c. . . Drainage port

2d. . . Slot body

2s. . . Screw

2w. . . Washing water inlet

3. . . Extruder

4. . . Extruder

Claims (13)

A method for producing an ethylene-vinyl alcohol copolymer, characterized by comprising a main washing step, wherein: comprising an ethylene-vinyl alcohol copolymer and a weight of 3 to 200 parts by weight relative to 100 parts of the ethylene-vinyl alcohol copolymer The glue of the alcohol is introduced into the horizontal washing tank, and in the horizontal washing tank, it is brought into contact with the washing water, and a shearing force is applied and twisted to repeatedly replace the surface and the inside of the mortar. A part or all of the alcohol was discharged to the outside of the tank together with the washing water to obtain an ethylene-vinyl alcohol copolymer aqueous composition having an alcohol content of less than 10 parts by weight based on 100 parts by weight of the ethylene-vinyl alcohol copolymer. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1, wherein the horizontal washing tank is disposed to be inclined from an upper direction to a lower direction along a flow direction of the paste in the horizontal washing tank. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein a ratio of a bath ratio of the horizontal washing tank to a washing water/introduction gel is 0.5 to 10. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the horizontal cleaning tank has a screw which is sheared in a vertical direction with respect to a longitudinal direction of the horizontal washing tank. Force, the screw has a gap of 1~20mm. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the amount of dealcoholization of the paste comprising the ethylene-vinyl alcohol copolymer and the alcohol in the horizontal washing tank is an introduction level washing The alcohol content of the glue before the clean tank is 80 to 100% by weight. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the residence time of the paste comprising the ethylene-vinyl alcohol copolymer and the alcohol in the horizontal washing tank is 0.5 to 10 hours. . The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the washing water of the main washing step comprises a carboxylic acid, a carboxylate, a boron compound, and a phosphoric acid compound. At least one additive. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the ethylene-vinyl alcohol copolymer aqueous group obtained in the main washing step The water content of the product is 30 to 400 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the paste supplied to the main washing step comprises a cement of an ethylene-vinyl alcohol copolymer, an alcohol, and water. Its water/alcohol ratio is from (1/99) to (70/30). The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, which comprises a preliminary washing step, wherein: before the main washing step, the ethylene-vinyl alcohol copolymer is contained The alcohol solution is introduced into a washing container, and is brought into contact with water or steam in the washing container, and a part of the alcohol is discharged together with water or steam to the outside of the container to obtain an ethylene-vinyl alcohol copolymer. Alcohol, and water cement. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, which has a step of preparing a granule, wherein: the ethylene-vinyl alcohol copolymer obtained in the main washing step contains a water-containing composition The material was supplied to an extruder, and after melting the crucible, it was extruded and cut to obtain pellets of an ethylene-vinyl alcohol copolymer. The method for producing an ethylene-vinyl alcohol copolymer according to claim 11, wherein the water content of the particles of the ethylene-vinyl alcohol copolymer obtained in the step of preparing the particles described above is copolymerized with respect to ethylene-vinyl alcohol. The weight of the object 100 is less than 10 parts by weight. The method for producing an ethylene-vinyl alcohol copolymer according to claim 11, wherein the particles of the ethylene-vinyl alcohol copolymer obtained in the step of preparing the particles described above are dried at 150 ° C for 5 hours. The content is less than 0.3 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer.